The 73-year-old rocker welcomed his eighth child, but the first with much-younger ballerina girlfriend Melanie Hamrick, on Thursday, his rep told Page Six.

“Melanie Hamrick and Mick Jagger’s son was born today in New York and they are both delighted,” the rep said. “Mick was at the hospital for the arrival.”

The rep added that both Hamrick, who is more than 40 years Jagger’s junior, and the baby are “doing well,” and noted, “We request that the media respect their privacy at this time.”

In September, friends of the Rolling Stones frontman told The Post he had mixed emotions about becoming a dad again. “He hasn’t responded to people sending him congratulations,’’ said one pal. “Family is extremely important to him, and he is unhappy at the thought that when he should be teaching his kid to play catch, he’ll be 80 years old.’’

The pair began dating in 2014, reportedly reconnecting after his former longtime girlfriend, the fashion designer L’Wren Scott, committed suicide.

Jagger is also a grandfather. He shares children with exes Marsha Hunt, Bianca Jagger, Jerry Hall and Luciana Gimenez Morad — the oldest of whom, Karis, is in her 40s.